1. Field of Invention
The present invention relates to a head lamp device for a vehicle.
2. Description of Related Art
A vehicle normally includes a head lamp device arranged at its front center. Although most of the front head lamp devices are of a single-lamp type, some are of a multiple-lamp type which include two or more lamps aligned relative to each other. For example, Japanese Utility Model Publication No. Sho 63-9493 entitled xe2x80x9cAn Automobile Head Lamp Devicexe2x80x9d discloses a pair of lamp units 16, 16 arranged side by side, as shown in FIG. 5 thereof.
FIG. 12 is a cross-sectional view of a conventional head lamp device including two lamps that are vertically arranged. This device has a structure in which filament bulbs 102, 103 are attached vertically to a lamp housing 101, and are respectively enclosed by reflectors 104, 105 having a substantially hemispheric shape. The front opening of the lamp housing 101 is covered by a front lens 106.
Note that the filament bulbs 102, 103 are general light bulbs having a filament as a light source. Inside the light bulb, a halogen gas is enclosed in order to suppress degrading of the filament. A halogen lamp is a typical example of such a light bulb.
On the other hand, a head lamp is obliged to perform the function of serving as a driving beam (hereinafter referred to as xe2x80x9chigh beamxe2x80x9d) and also as a passing beam (hereinafter referred to as xe2x80x9clow beamxe2x80x9d). Thus, one of the filament bulbs 102, 103 may be used as a high beam, while the other may be used as a low beam.
In this case, when using a low beam, only one bulb is turned on. Therefore, in order to obtain the necessary amount of luminous flux, a bulb of a large capacity or a reflector of a large size is needed. In order to install such a bulb or a reflector horizontally or vertically, the front lens inevitably has to be large. This makes it difficult to achieve the appearance desired for a vehicle.
Alternatively, a discharge lamp may be used, instead of a filament bulb, which can obtain a larger amount of luminous flux for lower power consumption. (For example, Japanese Patent No. 2542962). Discharge lamps employed for both of the two lamps will constitute a brighter head lamp which projects a front area of the same size. However, such a lamp results in increased weight and costs since each requires one high voltage generation circuit for lighting a discharge lamp.
In this view, the present invention aims to provide a head lamp device of a multiple-lamp type in which a high beam and low beam are generated by using separate bulbs. In particular, in such a device, the front lens thereof can be maintained at the desired area, or the necessary amount of luminous flux can be easily obtained. Moreover, an increase in demand and costs can be reduced.
In order to achieve the above object according to the present invention, there is provided a head lamp device for a vehicle, comprising a number of lamps each having a front lens, a bulb, and a reflector of a substantially hemispheric shape, wherein at least one of the lamps is a discharge lamp including a discharge bulb, and the remainder are filament lamps including a filament bulb, the filament lamps have a larger front-view area relative to the discharge lamp(s).
As a discharge lamp generates two or three times as much luminous flux as that generated by a filament lamp, an area taken up by a discharge lamp can be reduced to 60 to 70% of that which would be reserved for a filament lamp in order to generate the same or more light. As a result, the area for a filament lamp can be enlarged to 130 to 140% so that the filament lamp generates a sufficient amount of luminous flux.
That is, an amount of luminous flux as generated in the past can be generated by a head lamp with a front projection area that is smaller by several tens of %, or a head lamp with a front projection area as in the past can generate a larger amount of luminous flux by a few tens of %. For example, although a front projection area can be reduced when a project ion lamp is used for at least one of the two lights, the depth of the head lamp device tends to be larger. According to the present invention, the depth of a head lamp device remains small. Moreover, only a small number of lighting circuits are necessary compared to a case when two or more lighting bodies are all discharge lamps. That is, an increase in weight and costs can be suppressed since the number of lighting circuits is smaller than that of lighting bodies, namely, the number of light sources.
According to the present invention, the discharge lamp and the filament lamp are arranged horizontally in a direction of the vehicle width so that a boundary between the discharge lamp and the filament lamp is offset towards the direction of vehicle width from a vehicle center.
Since a discharge lamp can be reduced in size, while a filament lamp can be enlarged, a head lamp device which generates a larger amount of luminous flux can be realized while maintaining a constant height and width of a head lamp device.
According to the present invention, the discharge lamp and the filament lamp are arranged vertically so that a boundary between the discharge lamp and the filament lamp is offset either upwardly or downwardly from a center in of the height of both lamps.
A head lamp device having a screen light distribution can easily achieve elongated light distribution characteristics. Each lamp has an elongated shape as a result of the lamps being arranged vertically, and preferable light distribution characteristics can therefore easily be achieved.
According to the present invention, the discharge lamp is used for a driving beam or high beam.
Since a discharge lamp which generates a larger amount of luminous flux is for the high beam, to illuminate a further distance, a broader area can be illuminated more brightly than with a filament lamp.
According to the present invention, a discharge lamp is used for a passing beam or low beam.
Since a discharge lamp which generates a larger amount of luminous flux is for a low beam, a sufficient amount of luminous flux can be generated despite the presence of a shielding plate used to bring about low beam light, and thus a more distant, broader area can be lit more brightly than with a filament lamp.
According to the present invention, the discharge lamp is arranged on a side of the center line of a road, and used for a driving beam or high beam.
The provision of a discharge lamp as a high beam on a side closer to the center line of a road inevitably achieves a low beam arranged farther from oncoming cars. This arrangement is preferable in that the low beam, which is used when the vehicle passes an oncoming car, causes the oncoming cars to be illuminated less as it is positioned far from the oncoming cars. Also, by placing the low beam closer to a sidewalk, pedestrians walking on the sidewalk can be easily recognized.
According to the present invention, the discharge lamp is arranged on a side of the shoulder of a road, and used is for a driving beam or high beam.
The provision of a discharge lamp as a high beam on a side closer to a shoulder inevitably achieves a low beam arranged closer to the center line of a road. The low beam can illuminate a road surface, including the center line, substantially equally on the right and left sides. Although the high beam lights an area farther from the center line, displacement is negligible as the illuminated area is far from the driver.
According to the present invention, the discharge lamp is arranged on an upper stage, and used for a driving beam or high beam.
The provision of a high beam for illuminating farther areas above a lower beam for illuminating closer areas can easily achieve preferable light distribution characteristics. Also, with a vehicle covered by a cowling that approaches the horizontal as it goes up, a filament lamp for a low beam is attached at a place closer to the vertical, while a discharge lamp for a high beam is attached at a place closer to the horizontal. The positioning of a low beam that requires severer light distribution characteristics as compared to a high beam is therefore much improved and preferable the overall light distribution characteristics can therefore be maintained.
According to the present invention, the discharge lamp is arranged on a lower stage and is used for a driving beam or high beam.
A discharge lamp requires a lighting circuit for generating a high voltage, which is very heavy. If the discharge lamp is then arranged at a lower stage with the heavy lighting circuit arranged alongside, the center of gravity of the vehicle can be lowered and a cord connecting with the discharge lamp can be shortened.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description